OpenVMS Command Definition, Librarian, and Message Utilities Manual

This manual, published in January 2005, describes three core utilities within the HP OpenVMS operating system:

1. Command Definition Utility (CDU):

   • Purpose: Enables programmers and users to create, delete, or modify command definitions in OpenVMS DCL (Digital Command Language) command tables. These tables are crucial for the DCL interpreter to parse and execute commands.
   • Functionality: Users write command definition files (.CLD) to define new command verbs, their parameters, qualifiers, and keywords. It allows specifying the image or routine to be invoked, defining custom value types, and managing command syntax variations (DEFINE SYNTAX). It also includes features to disallow certain command combinations (DISALLOW) and generate object modules (MODULE, IDENT) for custom programs.
   • Usage: Invoked via the SET COMMAND DCL command, which can add/replace definitions (/REPLACE), delete them (/DELETE), or create object modules (/OBJECT). Programs can interact with parsed commands using CLI routines like CLI$PRESENT and CLI$GET_VALUE.

2. Librarian Utility (LIBRARIAN):

   • Purpose: Provides tools to create, access, and maintain various types of libraries on OpenVMS platforms. Libraries store frequently used modules of code or text.
   • Library Types: Supports Object libraries (.OLB), Macro libraries (.MLB), Help libraries (.HLB), Text libraries (.TLB), and Shareable Image libraries (.OLB).
   • Functionality: Users can create new libraries (/CREATE), insert or extract modules (/INSERT, /EXTRACT), delete modules (/DELETE), list library contents (/LIST), and recover disk space (/COMPRESS). It also allows for storing libraries in a data-reduced format (/DATA=REDUCE) to save disk space. Help libraries require specific input file formatting for topics and subtopics.
   • Usage: Invoked via the LIBRARY DCL command with various qualifiers to specify operations (e.g., /HELP, /MACRO, /OBJECT, /SHARE, /TEXT). Programs can also call LBR routines for direct library manipulation.

3. Message Utility (MESSAGE):

   • Purpose: Allows users to create custom messages that supplement OpenVMS system messages, providing feedback for errors, successful operations, or other conditions within their applications.
   • Message Structure: Messages follow a standard format: %FACILITY-L-IDENT, message-text, where FACILITY is the component name, L is the severity level (Success, Informational, Warning, Error, Fatal/Severe), IDENT is a unique symbol, and message-text explains the condition. A 32-bit message code is generated.
   • Functionality: Messages are defined in message source files (.MSG) using directives like .FACILITY, .SEVERITY, .BASE, and specific message definitions. These source files are then compiled into object modules.
   • Usage: The MESSAGE DCL command compiles .MSG files into .OBJ files, which are then linked with the application's object modules. The utility also supports message pointers (/FILE_NAME qualifier), allowing message text to be stored separately from global symbols, facilitating multilingual support or easier updates without relinking the main executable. The SET MESSAGE command can be used to control message display or load supplementary message data.